Fluoroketals and their preparation



United States Patent FLUOROKETALS AND THEIR PREPARATION Howard E. Simmons, Jr., Fairfax, Del., assignor to E. L du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application May 3, 1956 Serial No. 582,348v

3 Claims. (Cl. zen-340.7

This invention rel'atesto a new class of ketals and,

,more particularly to the cyclic ketals of selected fpreparation of new materials for transformer fluids.

Other objects will appear hereinafter.

These objects are accomplished bythe present invention of the cyclic ketals of wholly carbon chain glycols, any substituent of which is halogen and which has .a

chain of up to four carbons between the hydroxyls and carbon a cyclic ketal structure of from four to seven ring members. Preferably R,, and R contain no more than six'carbons each and together. contain no more than seven carbons and R, contains no more than nine carbons.

The newketals of this invention not only are notable for the surprising stability they exhibit under a variety of conditions but also for the peculiar process conditions by which they are made. The conventional ketal-forming reactions generally employ acidic conditions. These have beenfound to be ineffective to prepare the ketals of this invention. Surprisingly, the ketal-forming condensation between the requisite a,a-difluoroperhalogenoketone and the cycliejketal-forniing glycol derivative must be carried radical, is reacted underbasic conditions with the ec,oc'-

has a total of one to twelve carbons, with wholly carbon 1 'chain polyfluoroperhalogenoketones wherein each of the carbons immediately linked to the ketone carbonyl carbon carries at least one fluorine atom, with the remaining 'substituents on both said carbons and on all carbons linked thereto being halogen of atomic number no greater than 53 and preferably from 9 to 35. The new cyclic ketals of this invention are alternatively described as 2,2- disubstituted-l,3-dioxacycloalkanes wherein both 'of' the wholly carbon chain 2-substituents are directly and singly linked to the Z-carbon of the heterocyclic dioxacycloalkane ring through carbon carrying at least one fluorine substituent, with the remaining substituents on both said linking carbons and on any carbons linked directly thereto being halogen of atomic number no greater than 53 and preferably from 9 to 35. The compounds of this invention are 1,3-dioxacycloalkanes wherein the Z-ca-rgreater than 53 and preferably from 9 to .35,,and in' which the first or alpha-carbon of each radical, i.e., the carbon directly and singly linked to the indicated cyclic ketal or 2-carbon of the 1,3-dioxacycloalkane structure, carries at least one fluorine substituent and R, is a divalent hydrocarbon or halogenohydrocarbon radical of up to twel-vecarbons and of up to four chain carbons between the free valences, -i.e., so as to form with the two indicated ketal oxygens and the intervening annular difluoroperhalogenoketone. The requisite ketal-forming glycol derivative corresponds in its main carbon chain, i.e., that between the hydroxyl and the ester group, to the divalent radical which together with the abovedescribed Z-carbon and the 1- and 3-oxo oxygens forms the cyclic ketalor 2,2-disubstituted-1,3-dioxacycloalkane structure.

The following examples in which parts are by weight are illustrative of the invention.

Example I To .50 parts of syrn.-dichlorotetrafluoroacetone cooled to ,0- C. was addedslowly with stirring under anhydrous conditions ZOZ parts of ethylene chlorohydrin (ii-chloroethyl alcohol). The reaction mixturewas stirred for 15 minutes, and 35 parts of solid potassium carbonate was then added in small portions over a period of one hour. About 20 parts of n-pentane was added to facilitate mixing, and the reaction mixture was stirred for two hours at room temperature, at the end of which time parts of water was added. The resultant mixture was extracted with two SO-part portions of n-pentane. The extracts were combined, washed with water, and dried over anhydrous magnesium sulfate. After removal of the n-pentane solvent and distillation of the residue, there was obtained 51.3 parts (84% theory) of 2,2-bis(chlorodifiuoromethyl)-l,3 dioxolane, as a clear, colorless oil boiling at 171-l72 C. at atmospheric pressure; 11 1.3896.

Analysis.--Calculated for C H O CI F C, 24.7%; H, 1.7%; F, 31.3%. Found: C, 24.5%; H, 1.8%.

Another sample similarly prepared and purified exhibited the following analysis. Found: C, 24.9%; H, 1.9%; F, 31.4%.

In another related preparation, ethylene chlorohydrin and sym.-dichlorotetrafluoroacetone were mixed at icebath temperatures, and the resultant fichloroethyl hemi ketal was added 'dropwise, with stirring, to a cooled (0 10"C.) concentrated aqueous solution of potassium hydroxide. The reaction mixture was further stirred at ice/water bath temperatures and finally at room temperature. Upon extraction of the organic components with n-pentane and subsequent concentration and distillation, there was obtained 2,2-bis(chlorodifiuoromethyl) -1,'3-diox'olane in 29.5% yield. This illustrates the improved results achieved through use of substan tially anhydrous conditions. a

i i I Example 11 Fifty (50) parts of sym.-tetra chlorodifluoroacetone and dried over anhydrous magnesium sulfate.

3. added in small portions with stirring over a period of one hour. The resultant mixture was stirred for two hours at ice/Water bath temperatures and was allowed to stand overnight at room temperature. Water (100 parts) was then added, and the resultant mixture was extracted with two SO-part portions of n-pentane. The extracts were dried over anhydrous magnesium sulfate,

the n-pentane was removed, and after distillation of the Example III Freshly generated perfluoroacetone (ex. 30 parts of perfiuoroacetone hydrate and 60 parts of phosphorus pentoxide) was introduced as a gas at substantially room temperature beneath the surface of a mixture of 10.1 parts of ethylene chlorohydrin in about nine parts of n-pentane in a reactor equipped with a reflux condenser which was cooled with a solid carbon dioxide/acetone mixture. (about 60 minutes), ten parts of solid potassium carbonate 'was added in small portions over a period of about60 minutes, and the reaction mixture was stirred for one hour and then poured into 200 parts of water.

' boiling at 110-116 C. at 50 mm. pressure.

When refluxing of the reaction mixture stopped;-

The organic layer was extracted with three 25-part por- V tions of n-pentane, and the extracts were combined, washed with water, and finally dried over anhydrous magnesium sulfate. After removal of the solvent, there was obtained by distillation four parts (about 16% of theory) of 2,2-bis(trifluoromethyl)-l,3-dioxolane as an clear, colorless oil boiling at 99-100 C. at atmospheric pressure; 11 1.3247.

Analysis.Calculated for C H O F C, 28.6%; H, 1.9%; F, 54.3%. Found: C, 28.9%; H, 2.2%; F, 53.6%.

Example IV A mixture of 50 parts of sym.-dichlorotetrafluoroacetone, 32.6 parts of 1,3-dichloro-2-propanol (ex-chloromethyl-fi-chloroethanol), 35 parts of solid potassium carbonate and about 15 parts of anhydrous diethyl ether was stirred for about five hours at 25-30" C. using external cooling with an ice/water bath to control the exothermic reaction. Small portions of anhydrous diethyl ether were added periodically to maintain fluidity. The reaction mixture was poured into an excess of water with stirring and the resultant mixture extracted with diethyl ether. The ether extracts were separated and Upon concentration and distillation, there were obtained 51.3 parts (70% of theory) of substantially pure 2,2-bis(chlorodifiuoromethyl)-4-chloromethyl-1,3-dioxolane as a clear, colorless oil boiling at 74.0 C. under a pressure corresponding to 6 mm. ofmercury; 11 1.4186. The

product contained a small amount of a carbonyl-containing impurity which was removed by treatment with methanolic potassium hydroxide. The pure 2,2-bis- (chlorodifiuoromethyl) 4 chloromethyl- 1,3 dioxolane boiled at 100 C. under a pressure corresponding to 25 mm. of mercury; n 1.4179.

Analysis.-Calculated for C H 0 Cl F C, 24.7%; H,

1.7%; F, 26.1%. Found; C, 24.7%; H, 2.1%; F, 26.3%.

Under substantially identical conditions using approximately twice the proportions of the reactants and varying in that the reaction time was extended to about seven hours and the reaction mixture allowed to stand over- 4-chloromethyl-1,3-dioxolane was obtained in about of theory.

Example V mixture was poured with stirring into about 150 parts of water and the resultant mixture extracted with two 60-part portions of n-pentane. The combined pentane extracts were washed successively with three -part portions of water and one' 50-part portion of saturated sodium chloride solution. After drying over anhydrous magnesium sulfate, there was obtained on concentration and distillation 28 parts (49% of theory) of crude 2,2- bis(chlorodifiuoromethyl)-1,3-dioxane as a colorless oil Upon redistillation there was obtained 21 parts (37% of theory) of pure 2,2-bis(chlorodifluoromethyl)-1,3-dioxane as a clear, pleasant smelling oil boiling at 112-113 C. at 50 mm. pressure; n 1.4109.

Analysis.Calculated for C H O Cl F C, 28.0%; H, 2.4%; F, 29.6%; CI, 27.6%. Found: C, 28.1%; H,

V 2.6%; F, 28.5%; C1, 27.5%.

Example V1 To a cooled (-13 C.) solution of 24.3 parts of 2,2- bis(chlorodifluoromethyl)-1,3-dioxolane in about 300 parts of carbon tetrachloride was added 7.1parts (an equimolar proportion) of chlorine with stirring over a three-hour period under illumination from a commercial 275-watt ultraviolet lamp. The chlorine was added at such a rate as to maintain a faint yellow color in the reaction mixture. At the end of the chlorine addition, the solvent was removed by distillation under reduced pressure and there was thus obtained as a residue 25.2 parts (91% of theory) of the crude monochloro derivative.

Upon precision fractionation there was obtained 18.0 parts (65% of theory) of pure 2,2-bis(chlorodifiuoromethyl)-4-chloro-1,3-dioxolane as a clear, colorless liquid boiling at 179-181 C. at atmospheric pressure; 11 1.4093.

Analysis.-Calculated for C H Cl F O Cl, 38.2%; M.W., 275. Found: Cl, 39.4%; M.W., 290, 293.

Another chlorination carried out in identical fashion varying only in that a reaction temperature of 5 C. was

used afforded approximately similar results except that f the monochloro compound was contaminated by appreciable quantities of the dichloro compound. After two precision fractionations, the pure 2,2-bis(chlorodifiuoromethyl)-4-chloro-1,3-dioxolane was obtained as a clear, colorless liquid boiling at 179-180 C. at atmospheric pressure; n 1.4050.

Analysis.--Calculated for C H CI F O C, 21.6%; H, 1.1%;Cl, 38.3%; F, 27.4%; M.W., 275. Found: C, 21.9%; H, 1.4%; Cl, 37.6%; F, 27.5%; M.W, 258, 268.

Example VII As described in Example VI, 7.1 parts (an equimolar proportion) of chlorine was added to a solution of 24.3 parts of 2,2-bis(chlorodifluoromethyl)-1,3-dioxolane in about 300 parts of carbon tetrachloride over a period of three hours. The chlorine addition was continued for an additional 20 minutes, during which time it was found possible to add another 7.1 parts (a second moiar proportion) of chlorine. The solvent was removed by distillation under reduced pressure and there was thus obtained 31.6 parts (96% of theory) of the crude dichloro compounds. By precision fractionation, there was obtained 26.5 parts (85% of theory) of a mixture of 2,2 bis(chlorodifiuoromethyl) 4,4 dichloro 1,3- dioxolane and 2,2 bis(chlorodifiuoromethyl) 4,5 dichloro-1,3-diox0lane as a clear, colorless liquid boiling at I 16852-184 l. at. atmospherr .and showed the presence iii 'a "of chlorine wasadded with stir ng't a so Qf tWQ hours while maintainin'gfthe reacti I C. The solvent was removed 'by 1d 'fc pressure; n 1,4 159.. Nulear m'agneti'eresonanc spectra andiinfr'aredabsorption data indicated the rodnctto bethe indicated "isomers Analysisr calculated {for p C "0.7%; (:1, 45.5%; F, 24.41, p

20.4%; H,"0.'9%; Cl, 45.0%, 332. a, Example VEHI- As in Example VI, 21.3fpar'ts (3f molar proportions) lution; of 24: 3

reduced pressure and there, was thus obtained as a residue 326 parts (95% of theory)- ojff"the cru'd'e trichloro cdm pound. Upon: precision fraction 'omfth'erewaslobtained 202 parts (58% "Of th'eo'ryf 2 biS('ChlbTdiclar, colorless liquid botanist 99 -205 Cfat atmosex nip'ze 1 Example VIII was re eated-"var ing ofily inthat 's'llz '-part's (4.4 molarproportions)'ofchlorineiwas added oyer .arbup VI-A vof the period c table, especially those of sulfur, are preferred.

aperiod of"2.-5 "hou'rswhile inai-ntain'ing'the reaction mixtu'reat '50 C. Thesolyent remover by distilla- I a residue 379 parts (99% of'thep'ry) ur ne crude tetra- *chlforo compound. Upon precision fractionationgthere "oxol'an'eas a clear, colorless'zliqui'd boiling 91521 8 219" f Q a'bivale'nt organic'radical" iniwhich any substituent :is

halogen of atomic number no greater than 5-3 and pref- "ferahly no 'greaterthanf35 withf wholly carbon chain perhaItig'e'iIoketOneS, especially those aliphatic in character, Te; 21 halti'c, 'cy'cloaliphatic, 'or mixed aliphatic; cyc'loaliphatic -etohs, which perhalogenoketonescarry at least "one fiuo'rihe-a toi'n oneach of the alpha c2irbons,-i:e., the two carbons immediately linked to the ktone carbonyl. (Any such x,a' difluoroperhalogehoketone may b'ef'em "ployed including, inaddition't'othose given in the examples, polyfluoroperhalogeno aliphatic ketones, e=g.,;pe'r

"k'etorfies, perfliiorocyclopehtanone,:etcJ, v V 3 The preseiit' inveiitioh is-alsogene'ricto the preparation 'o'f -these cyclic ket als -by the reaction of these-manianeroper mle enesl nme with ;-n1 -hali-es"ters,-' with "monoand "polyhasic, 2 or anic and in'or'ganic" acids, jo'f I tion under reduced p're's'siir'e and thefefwas obtained as QThes'e ketal fjorming glycolderivatives canbe described 5 any 1he=following structural tormula:

i a v IL 1o fwherein the 'R s; whichjcan he alike or difierent, are used to represent hydrogen, hydrocarbon, (including aliphatic, aromatic, cycloaliphatic, ara l iphatic, a'lkaromatic),.halo- -gen o f atomic number=no- ;greater than 53, and prefer- .ably from 9 to 35., or; halogenohydrocarbon where the ghalogen is as:ahovegn isused.tof;represent a small, preferab ljplural, integer .preferably-two orthree, and;- X is halogen of atomic I greatengenerallythan four and number 'notgreaterthan zajndpreferably from 9 to 35,

orthe neutral n onoyalent' cation iofqa. strong oxygencontaining acid, most preferably of sulfur, linked'to the Lindicated carbOn.chain diradicalthrough ester oxygen.

. involyediin theseketal-formitotaln be 'ofr n'a chain ,carbons b'efreadier availability 'the nece'ssary iintermediatesi the "i.e.,the'dioxolanes and 'dioxanejs, especiallyjhe former.

Any "such glycolghalf-ester may. be employed include in'g not only those showniinfthe examples above but also: ,hal'o'hydr'ide half-estersfiof alkylene glycols, e.g., 2-chIoro-' 1'-propanol," tetramethylenechlorohydrin, -e tc.; 'halohy'dride half-esters jofiaromatic substituted alkylene glycols', eg B-phenyl-pwliloroethyl jal'cohol, etc.;' halohydride half-esters of cycloaliphatic-substituted 'alkylene *cols, e.g., 2-bro'rn'oe1-bromornethyl'ethyl alcohol,'etc;; halo- 7 glycols wherein'the hydroxyls are connected'by'anbiyalent -hydrocarbon radicalg-any substitu'e'nt onwliihis'a'h'alm *gen o-f atomicnumber not greater'than SB 'and preferably nor-greater than 35. Because of' the'ir greater' rethe Stiig';oxygen-containing acidsfdfdlie elements' of ,glyc'ols, e.g'., 1-hydroxymethylcyclohexyl chloride, jetc.;

'halohydride half-esters 0f arailiphatimsubstituted alkyl'ene V glycol's, 'e.g. ,1flbenzyhfichloroethyl "alcohol, etc.; haloliyd'ride "half-esters of 'alkarornatic-substituted alkylene glycols, e.g., fl ptolyl-fi-fchloroethyl, alcohol, e'tc.; halo- -hyd'ride half-esters of halogen-substituted alkylene glyhydride half-esters off 'cycloalipha'tic' glycols and substituted glycols, eZg., 2-chlorocyclohexanol, etc.; half-esters of the above glycols and substituted glycols with the strong oxygen-containing .aci'ds, e;g.,e Z-hydroxyethyl v 'methyls'ulfate, 2 hydroxyethyl vp toluen'e-sulfonate, etc.

The new ket'a ls of this' inyent ion are prepared by'direct condensation offthe aforesaidfpolyliuoroperhalogenoketone's and the glycol fhzilfes'terfin the presence of a base, preferablyan inorganic salt jo'f .a strong base and I aweak acid." These three st'antially equirnolarproportio s.

the latter two are Tg'ene y used "to facilitate reaction.

The 'ketal-forming' gly 'lfderiyatiye isfgen'erally notaused' "in gover' 50% excess lbuftith present in 'arriourits uplto %1'7exeess}.

greater than 4. Suitable specifi'c ex'ampl'es include' the carbonates, bicarbonates, hydroxides, cyanides', "acetates, "benzoates, *etc. Because of. readier availability' f'and However; excesses of x lated and purified by conventional procedures.

- assign.

greater reaction eflici'ency. the alkali metal and alkaline earth metal salts are preferred. The most common of 'these are the lithium, sodium, potassium, magnesium,

calcium, and barium carbonates, bicarbonates, hydroxides, and acetates.

The reaction can be effected properly in the presence or absence of an aqueous or wholly organic reaction medium. For reasons of increasedyields, the reaction zone ispreferably maintained under anhydrous'condh.

liquid organic .diluent can be used, and generally speaking the most common are employed, e.g., the normally 1 liquid hydrocarbons and halogenatedhydrocarbons, including the aliphatic and halogenated aliphatic compounds, such as: the hexanes, the heptanes, the octanes,

the various chlorinated aliphatic hydrocarb'ons,including carbon tetrachloride, te'tra'chloroethylene, the chloropentanes, and the like; the aromatic and halogenated aromatlc hydrocarbons such as benzene, toluene, the

xylenes, chlorobenzene, and the like; the cycloaliphaticand halogenated cycloaliphatic hydrocarbons, e.g., cyclohexane, chlorocyclohexane,'and the like. The choice of the particular inert diluent .is not at all critical, and

. will vary primarily with the reaction temperature, found necessary. a

The condensation is-carried out at temperatures ranging from below to generally no higher than 200 C.,

varying with the relative reactivity of the particular polyfluoroperhalogenoketone and the particular ketal-forming glycol derivative thereof being used. I Thus, with the short-chain ketones and the short-chain ketal-forming glycol derivatives of no more than a total of about six to eight carbons each, the reaction can be carried out'at temperatures from generally no lower than about 25 C.

to about 50C. Practically speaking, the reaction can be effected in most instances over the range 0100 C. The pressure at which the reaction is carried out is 'largely immaterial and will vary, as will be apparent to vthose skilled in the art, with the specific nature of the reactants and the operating temperature being used, i.e., temperature and pressure are interdependent variables apparent for each particular system. Thus, if a lower boiling reactant .is used and a higher reaction temperature is desired, eflicient condensing means must be supplied to insure retention of that reactant in the reaction zone, or, alternatively, thereaction must be carried out in a closed reactor under superatmospheric pressure.

After the initial condensation is effected, the precipitated inorganic salts can be removed from the reaction mixture by simple filtration, and the product can be iso- A simple method of carrying out these same steps, particularly in those instances where a liquid organic diluent is used and the precipitated inorganic, salts are water-soluble, is'to treat the entire reaction mixture with an excess of water, whereby the salts dissolve in the aqueous layer and the organic material including the product remains 'in the organic layer. Simple separation of the latter, followed by distillation and/or crystallizationgenerally affords the desired ketals directly in high purity.

By employing the above described methods there may be prepared further cyclic ketals of the present invention. Thus, 2,2-bis(chlorodifluoromethyl) 4 methyl-1,3-dioxolane is obtained from 2-chloro-1-propanol and sym.-

Any inert dichlorotetrafluoroacetone; 2,2 bis(dichlorofluoromethyl)-l,3-dioxepane is obtained from tetramethylene chlorohydrin and syn-1.-tetrachlorodifluoroacetone;v 2,2-bisdioxolane (also identified as 2,2-bis(ch1orodifluoromethyl)-l,3-dioxaspirol4.5ldecane) is obtained from l-hydroxymethylcyclohexyl'chloride and sym.-dichlorotetra- 1,3-dioxolane. is obtained from fi-benzyLfi-chloroethyl alcohol and sym.-dichlorotetrafluoroacetone; 2-pe'rfluoroethyl-2-perfiuoropropyl-4ep-tolyl-1,3-dioxolane is obtained from B-p-tolyl-B-chloroethyl alcohol and perfluoroethyl perfluoropropyl ketone; 2,2-bis(perfluoropropyl) 4-bromomethyl-l,3-dioxolane is obtained from 2-bromo1- bromomethylethyl alcohol and bis(perfluoropropyl) ketone; 2-perfiuoromethyl2-perfluoropropyl-4,5-hexahydrobenzo-1,3-dioxolane (also identified as B-perfluoromthyl- 3-perfluoropropyl-2,4-dioxabicyclo[3.4.0]nonane) is obtained from 2-chlorocyclohexanol and. perfluor omethyl perfluoropropyl ketone; 2-perfluorocyclohexyl2-perfluoromethyl-l,3 dioxolane is obtained from Z-hydroxyethyl methylsulfate and perfluorocyclohexyl perfluoromethyl ketone; and 2,2-octafiuorotetramethylene-1,3-dioxolane (also identified as 5,5,6,6,7,7,8,8-octafiuoro-1,4-dioxaspiro[4.4]nonane) is obtained from 2-hydroxyethyl-p ftoluenesulfonate and perfluorocyclopentanone.

The new cyclic ketals of this invention, i.e., ketals. of

wholly carbon chain 'glycols with polyfluoroperhalog enoketoneswherein both the. carbons immediately lmkedto the carbonyl carbon carry at least one fluorine .sub-

stituent, are markedly dilferent from previously known ketals, even including those of perhalogenoketones not containing the two necessary alpha-fluorine substituents. The differences are fundamental, extending even to'the possibl emodes of preparation of the ketals. Thus the conventionalroutes to cyclic ketals, e.g., the direct interaction of a glycol with a ketone or the interaction of an orthoester and a ketone using strong acid catalysts ,such as hydrogen chloride, p-toluenesulfonic acid and the likesee methods 129 and 130, pages 261-264, Wagner and Zook, Synthetic Organic Chemistry, Wiley, 1953-- do not have bonded thereto the necessary fluorine substituent, no ketals are obtained. Thus,-when hexachloroacetone and ethylene chlorohydrin were mixed at 0 C., treated with solid potassium carbonate, stirred and extracted, all in the detailed manner illustrated in the foregoing examples, no, 2,2-bis(trichloromethyl)-1,3-diox-- olane, i.e., the cyclic ketal, was obtained. The only product which could be isolated was the fi-chloroethylester of trichloroacetic acid as a clear, colorless liquid, boiling at 57 C. under a pressure corresponding to 0.2 mm. of mercury; n 1.4782.

.Analysis.Calculated for C H O Cl C, 21.30%; H, 1.80%; Cl, 62.8%. Found: C, 22.10%; H,,2.00%; CI, 62.7%.

Thus, when the ketone does not have necessary fluorosubstituent on each m-carbon, the necessary basic synthesis fails, and only products arising from haloform cleavage result.

The new cyclic ketals of this invention rangefrom clear, colorless, pleasant-smelling liquids to low-melting solids, depending generally on the total number of car- Jbons in the molecule. Generally speaking, those containing less than about 18 carbons are clear, colorless, pleasant-smelling liquids boiling normally from 100- 300 0.;

Most surprising properties of the new ketals of the present invention are their extreme chemical and physical stability, and especially their extreme hydrolytic stability. In general ketals are extremely sensitive to'aqueous acid with ready hydrolysis to the starting aldehyde and alco- 1101. .Thus, in the preparation of ketals according to Wagner and look, supra, the various acidic catalysts must be very carefully neutralized or otherwise removed before the necessary continuing aqueous workup, otherwise the V ketals would not be obtained. In surprising contrast,

the present ketals show substantially no reaction with aqueous "acids even at elevated temperatures. More specifically, the cyclic ketal of Example I [2,2-bis(chlorodifluoromethyl)-1,3-dioxolane], a typical representative of this new class of ketals, was heated at the reflux for eighteen hours in methanol containing 67 volume percent of aqueous concentrated hydrochloric acid, and 98% of the ketal was recovered. The recovered material, even after precision fractionation, amounted to about 92% of ketal charged and exhibited an 11 213899 as compared with 1.3896 for the starting material.

Another sample of 2,2-bis(chloiodifluoromethyl)-1,3

dioxolane, similarly prepared and exhibiting arefractive indexn 1.3908, was treated under the following conditions with no observable change and with the indicated refractive indices respectively obtained on the treated sampleafter recovery: i

' (a) 9 M sulfuric acid at 160 c. for 96 hours;

(b) 8 M nitric acid at 160 C. for 96 hours; n 1.3908

(c) Concentrated hydrochloric acid at 120 C. for 96 hours; 11 1.3908

(d) 20% aqueous potassium hydroxide at 80 C. for 24 7 hours; n 1.3904 These'new ketals are not only stable to acids but show no reaction with variou-s'metals,' either insolventsor to the metal alone, including exposure at elevated temperatures. More specifically, a representative'ketal [2, 2- bis(chlorodifluoromethyl)-1,3-dioxolane] failed to undergo any reaction with metallic zinc in isoamyl alcohol or with metallic magnesium in diethyl ether or in di-n-butyl ether. Similarly, upon heating the same ketal in the presence of zinc dust, magnesium powder, or copper,

powder, no evidence of reaction was obtained.

7 The extreme stability of these new polyfluoro-containing ketals is based on the fact that each of the carbons immediately linked to the 2-carbon of the ring, i.e., the

carbon between the two ketal oxygens, carries at least' one fluorine substituent. The stability of these ketals is not a function of fluorine content alonebut is a function of fluorine content and position of the fluorine substituents. Thus, 2-trifluoromethyl-1,3-dioxolane, i.e., the the cyclic acetal of trifluoroacetaldehyde, which does not fulfill the above requirement, was obtained readily as a clear, colorless liquid, boiling at 91.5-92 C. at atmospheric pressure and exhibiting a 11 1.3365, by the'con- 7 "densation of trifluoroacetaldehyde hydrate with ethylene chlorohydrin in the presence of magnesium sulfate, followed by treatment with anhydrous solid potassium carbonate. This compound has only one fluorine-substituted carbon bonded directly to the carbon carrying the ketal oxygens. In contrast to the behavior exhibited by the ketals of the present invention, hydrolysis of this acetal with methanolic hydrogen chloride resulted in complete destruction of the compound.

. The new ketals ofthis invention exhibit not only surprisingly high hydrolytic stabilitybut also outstanding resistance against thermaland oxidative degradation, and are in fact non-flammable. Furthermore, they possess.

sufliciently high boiling points so as to make them of utility in certain so-called stable liquid-outlets, e.g., as transformer fluids, as fluids for high'temperature power transmission or hydraulic systems, or for use. in liquid coupled mechanical drives, and the like, where a particularly high degree ofoxidative and hydrolytic stability is needed at elevated temperatures.

Thus, the 2,2-bis(chlorodifluoromethyl)-1,3-dioxolane of Example I, a representative member of the class of I cyclic ketals of this invention, was heated at the reflux (172' C.) at atmospheric pressure for 125 hours with a stream of air being bubbled'through the boiling liquid.

I At the endof this time a very faint light-yellow coloration was noted as the only change in the liquid ketal. There was recovered 86.5% of the starting ketal, the losses being due to a relatively inefficient condenser and entrainment by air. The initial sample of the ketal exhibited a refractive index at 25 C. of 1.3895 and an n of 0.008 as determined in' a 1.8% solution in benzene. The material remaining at the end of the 125 hours exhibited values of 1.3899 and 0.009, respectively,

as determined in identical fashion.

The term substituent is used herein in its ordinary sense ;to indicate a replacement for hydrogen on carbon.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations are to be understood therefrom. The invention is not limited to the exactdetails shown and described for obvious modifications will occur to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. 2,2-bis(chlorodifluoromethyl)-1,3-dioxolane.

2. 2,2-bis(dichlorofluoromethyl)-1,3-dioxolane.

3. 2,2-bis(trifluoromethyl) 1,3:dioxolane.

4. 2,2 I- bis(chlorodifluoromethyl)-4-chloromethyl-1,3-

' dioxolane.

5. 2,2-bis(chlorodifluoromethyl)-1 ,3 dioxane. 6. The process for preparing cyclic ketals which comprises reactingtogether a base, a perhalogenoketone having fluorine on each carbon linked directly to the ketone carbonyl, and a half ester of a glycol selected from the class consisting of hydrocarbon and halohydrocarbon glycols with up to 4 carbons between the hydroxyl groups and a total of up to 12 carbons and an acid of the class consisting of hydrohalic acids and strong oxygen-containing acids of an element of group VI-A of the periodic ta le.

ethylene glycol and the ketone is a perh-alogeno acetone.

8. A compound of the group consisting of 1,3-dioxolanes, 1,3-dioxanes and 1,3-dioxepanes wherein (1) the 2-carbon carries a member of the group consisting of twomonovalent perhalogenated hydrocarbon radicals of no more than'7 carbons each and one divalent perhalogenated hydrocarbon radical forming with the 2-carbon a carbocycle of 5 to 7 ring carbons, (2) each carbon directly attached to the Z-carbon carries at least one fluorine, '(3) each heterocyclic ring carbon other than the 2- carbon carries two members of the group consisting of hydrogen, halogen, lower alkyl and lower haloalkyl, and (4) all halogen in the compound is of atomic number no greater than 53.

Kuhn: I. Prakt. Chem., vol. 156, pp. 103-49 (1940).

(See C.A., vol. 35 1763 7. The process of claim 6 wherein the half ester is of i 

5. 2,2-BIS(CHLORODIFLUOROMETHYL) -1,3-DIOXANE.
 8. A COMPOUND OF THE GROUP CONSISTING OF 1,3-DIOXOLANES, 1,3-DIOXANES AND 1,3-DIOXEPANES WHEREIN (1) THE 2-CARBON CARRIES A MEMBER OF THE GROUP CONSISTING OF TWO MONOVALENT PERHALOGENEATED HYDROCARBON RADICALS OF NO MORE THAN 7 CARBONS EACH AND ONE DIVALENT PERHALOGENATED HYDROCARBON RADICAL FORMING WITH THE 2-CARBON A CARBOCYCLE OF 5 TO 7 RING CARBONS, (2) EACH CARBON DIRECTLY ATTACHED TO THE 2-CARBON CARRIES AT LEAST ONE FLUORINE, (3) EACH HETEROCYCLIC RING CARNON OTHER THAN THE 2CARBON CARRIES TWO MEMBERS OF THE GROUP CONSISTING OF HYDROGEN, HALOGEN IN THE COMPOUND IS OD ATOMIC NUMBER NO (4) ALL HALOGEN IN THE COMPOUND IS OF ATOMIC NUMBER NO GREATER THAN
 53. 